I think we might be able to learn more about the evolution of our boats if we look carefully for the exact hull identification number. This is stamped into the electrical grounding plate on the inside centre of the transom. Depending on how the grounding wires are routed, the number may be completely covered by the wires and end rings.
For example, Catherine Ann is Alwest 370-72-181 which I interpret to be the 181st Alwest 370 (or maybe Alcan + Alwest) and was built in 1972.
Have a look, next time you are down to your boat.
Rob